The 1992 update of the Transportation Element recommends that a program be developed to address the concerns expressed by citizens and neighborhood associations throughout the City regarding the negative impacts of excessive traffic volumes and speeds on residential Neighborhood Collector Streets. On February 26, 1992, City Council adopted Ordinance No. 165132 authorizing program development and the testing of traffic management devices on NW Cornell Road and NE 15th Avenue as demonstration projects.
The NW Cornell Road Test Project was undertaken in April 1992 and the NE 15th Avenue Test Project began in August 1992. The major goals for the two test projects were:
Design, test, and evaluate traffic management devices that would improve residential safety and neighborhood livability on Neighborhood Collector Streets by mitigating the impacts of vehicular traffic on the streets while accommodating all modes of transportation.
Encourage citizen involvement and participation in all phases of the projects.
However, NW Cornell is one of only four through routes to the west of downtown Portland. The others are W Burnside, SW Fairview and US highway 26. Because of this limited access on the west side of Portland, NW Cornell functions more like a Major City Traffic Street by providing access from the surrounding area into the City's downtown commercial areas, or a Regional Trafficway by providing neighboring cities to the west of Portland a commuting route into town.
Currently, construction on Tri-Met's Westside Light Rail and Oregon Department of Transportation construction on US Highway 26 (Sunset Highway, a Regional Trafficway) has added more vehicles to all of the arterial and many of the local streets in the area.
The test project segment of NW Cornell Road extends from just west of NW 25th to just west of NW 30th. The street is 36 feet wide with curbs and sidewalks for most of the street segment and, except for a pair of sharp curves, is fairly straight with a grade of approximately 3 to 5 percent. There is one lane of travel in each direction and parking on both sides of the street. Only two Local Service streets, NW Westover and Summit, intersect with this segment of NW Cornell Road. Three pedestrian stairways and one school crossing are located along the street segment. The land use along the street segment is exclusively residential.
The appointed members of the NW Cornell Road Task Force was specified in the Ordinance that established the test projects and included Roger Eddy, Jim Edwards Bob Gibson, Michele Mass, John Phillips, and Howard Shapiro. This Task Force worked with staff to develop goals and objectives and define the project elements. Other interested parties also participated in the project.
BTM staff worked for nearly two years with the NW Cornell Road Task Force, the area neighborhood association, the Portland Fire Bureau, and other City bureaus to develop, test, and evaluate a traffic management plan incorporating new traffic management devices that accomplish the neighborhood's goals for the project. The four goals for the project (in order of importance to the committee) were:
- Reduce traffic volume.
- Reduce vehicle speeds.
- Enhance the neighborhood environment through noise reduction, increased safety, lower vehicle speeds, and the design of roadway surface modifications.
- Improve pedestrian safety.
The NW Cornell Traffic Committee's original goal was to reduce 85th percentile speeds to 25 mph. However, the Committee acknowledged that this goal may not be achievable and agreed that the project need not meet the stated goals to be a success. As part of this project goal, the Traffic Committee asked that the Department of Transportation's State Traffic Engineer rescind the 30 mph speed resolution to see if posting a 25 mph speed zone would have any effect on speeding on Cornell. City Staff advised the Committee that changing the 30 mph zone to a 25 mph zone would probably not change the actual speeds on Cornell. However, at the request of the committee, the City did request the State remove the 30 mph zone, allowing a return to the statutory speed of 25 mph in residential areas. The City then replaced the 30 mph signs with 25 mph signs.
The Traffic Committee also stated a goal of reducing traffic volumes on NW Cornell Road. However, diversion on a Neighborhood Collector was not allowed, as limiting access would not be in keeping with the designation and the Transportation Element. Nonetheless, the Traffic Committee hoped that by reducing the "attractiveness" of the street as a commuter route by installing the traffic calming project that commuters would choose alternate routes.
Following an extensive review of existing literature and research by BTM staff during program development, two new traffic management devices were chosen to be tested on NW Cornell Road.
In July 1992, three test 22-foot Arterial Speed Bumps were installed at 300-foot intervals along the straight, lower section of the street. At the existing school crossing, a test Median Island Slowpoint designed for a mid-block location was installed. In October 1992, a single 22-foot speed bump was installed to the west of the sharp curves on the upper section of the street. This 22-foot speed bump proved to be ineffective and was later removed due to resident complaints. A Rumble Strip test was installed in October, 1994 and removed due to complaints of increased noise from the residents. One additional 22-foot speed bump was installed at the western edge of the project area in the spring of 1995.
Since NW Cornell Road was a demonstration project undertaken prior to the completion of the Arterial Traffic Calming Program adoption by City Council, no ballot was taken. However, many residents expressed their support for the project to staff throughout the test and testified in favor of the project at the City Council hearing.
As stated previously, Traffic Calming projects on Neighborhood Collector Streets can not include any diversion since Neighborhood Collectors are designated to carry local traffic in and out of the neighborhood and limiting access would not be in keeping with the Transportation Element. Of particular concern to the project though, was any unintended shift of traffic from the Neighborhood Collector to any Local Service Streets. For this reason, volumes are measured both before and after a project is constructed to determine if any of the traffic prior to the project has shifted to other locations.
Prior to the project construction, volume along NW Cornell Road varied from approximately 5,500 vehicles per day to 7,200 vehicles per day. The lowest volume on Cornell was recorded east of NW Westover. Investigation of NW Westover indicated that a significant amount of eastbound traffic was leaving Cornell to continue eastward on Westover during the morning rush hours (7am-9am). This two hour period recorded 25 to 30 percent of the total 24 hour volume for the eastbound direction on this street.
After the traffic calming devices were installed on NW Cornell in late July of 1992, the location east of Westover increased in total daily volume by over 1,000 vehicles per day (VPD). At the crosswalk location (Pettygrove) volumes increased approximately 300 (VPD). The other three locations decreased in volume. Graph B illustrates these volume changes. The volume range after the project was in place was 6,000 VPD to 6,700 VPD. This is a much more even distribution than before the project began.
There is no explanation for the increase in traffic volume on NW Cornell east of 29th Avenue. Volumes on NW Westover had no corresponding decrease in traffic volume. The volume on Westover was less than 900 VPD before the Cornell Project, and slightly over 900 VPD after the project was built. Consequently, it is clear that the traffic calming devices on Cornell did not increase volumes on NW Westover.
Recent data collected on NW Cornell indicate a significant increase in overall volume for the road. The volume currently ranges from 7,100 VPD to 7,800 VPD. This increase was predicted as a result of traffic being diverted by construction projects on the Sunset Highway (26), and on the Westside Light Rail. However, an increase in new home construction to the west of NW 30th has also added to the new volume on NW Cornell.
Volumes on NW Westover have varied over the past four years, due to the same construction projects further east. The volumes are currently below 1,000 VPD, close to their original volume counts.
The standard gauge of traffic speed is the 85th percentile speed. This represents the speed not exceeded by 85 percent of the drivers, or more importantly, the speed that 15 % of the drivers are exceeding. The 85th percentile traffic speeds on NW Cornell Road prior to project construction ranged from 28 mph to 40 mph, depending on the specific location.
The 85th percentile speeds recorded soon after the test speed bumps and slow-point were installed were significantly lower than before the project began, with the exception of the location west of the school crosswalk just east of NW 29th Ave. This location had 85th percentile speeds of 26 mph eastbound and 30 mph westbound, before the project began. Immediately following the device installation, the 85th percentile speeds were 30 mph eastbound and 31 mph westbound. However, speed counts completed in April, 1996 indicate those 85th percentile speeds at the crosswalk location are now 24 mph eastbound, and 30 mph westbound.
As previously stated, all other data collection locations showed significant decreases in the 85th percentile speeds recorded before the project began. Graph A outlines these speed changes by location. Also significant are the smaller variations in speeds by locations. Prior to the project the 85th percentile speeds ranged from 28 mph to 40 mph, a 12 mph difference. Now the speed variations are 26 to 33 mph, a variation of just 7 mph. This indicates the pace of the traffic is more consistent over the length of the street, with fewer vehicles speeding and slowing from one location to another.
An additional speed bump had been requested by residents of Cornell. The bump requested would be northwest of the slow point, between NW 28th and NW 29th Avenue. Counts taken immediately following the speed bump construction showed that the 85th percentile speeds went from 26 mph eastbound and 30 mph westbound to 30 mph eastbound and 31 mph westbound. However, further increases in the 85th percentile speeds have not materialized. Traffic data gathered in April, 1996 recorded 85th percentile speeds of 24 mph eastbound and 30 mph westbound.
Pedestrian Safety and Neighborhood Livability
The lower speeds on Cornell appear to have improved the environment along this street as well as safety, in particular, pedestrian safety. There are more opportunities to walk along NW Cornell safely. The slow point at the school crosswalk has provided the pedestrian with a center refuge, allowing them to cross Cornell one lane at a time, if necessary.
This project has been successful in:
- Reducing vehicle speeds along NW Cornell Road. The 85th percentile speeds that were once in the 30 and 40 mph range have been replaced with 85th percentile speeds in the 20 and 30 mph range. The addition of the 22' speed bumps and the crosswalk slow point have had a positive effect on traffic speed reduction.
- Accomplishing the major goals of the test project. We have found that speed reduction on Neighborhood Collector Streets is possible, and for residential areas, quite appropriate. Neighborhood Collector Streets should continue to be included in the Traffic Calming Program.
This project was not successful in meeting the Traffic Committee's goals to reduce traffic volumes and traffic speeds to 25 mph.
As previously explained, traffic calming project designs for Neighborhood Collector Streets cannot include diversion. Consequently, traffic volumes were not decreased as a result of this project. In fact, the NW Cornell Road volumes have actually increased as a result of the Sunset Highway and Westside Light Rail construction. The volume increase due to the construction is expected to drop once the projects are complete. Further, completion of those projects may encourage some commuters to abandon their NW Cornell route in favor of using Highway 26, or they may even chose to leave their vehicles at home and ride the new Westside MAX.
While traffic volumes were not reduced on NW Cornell Road and the Traffic Committee's goal of volume reduction was not met, the project was able to calm traffic on Cornell without shifting traffic onto the Local Streets. Volume on NW Cornell did not shift to NW Westover, as had been feared.
The project was successful at reducing traffic speeds, although in some locations the reduction was not as much as the stated goal. Before the project began, the 85th percentile speeds along the street were measured in the 30 to 40 mph range. After the project was installed, the 85th percentile speeds were measured in the 20 to 30 mph range. The additional speed bump requested by residents to be placed between NW 28th and NW 29th would produce no additional slowing, as the 85th percentile speeds near the proposed location were measured at 24 mph eastbound and 30 mph westbound. An additional speed bump may serve as an annoyance to residents adjacent to the bump. Therefore, it is recommended that no additional speed bumps be added to NW Cornell Road.